The personal digital assistants (PDAs) will also allow road policing officers to issue fixed penalty tickets atthe roadside and for this information to be sent electronically to the Central TicketOffice.
Shashi Verma, TfL's director of customer experience, said: ''Pay as you go Oyster cards do not expire and customers are able to return their cards to a Tube ticketofficeat any time for a refund of the remaining balance and card deposit.